In recent years, increasing amounts of radioactive wastes are being generated from nuclear power facilities such as nuclear power plants, as well as medical facilities, universities and laboratories that use radioisotopes. Accordingly, reliable measures for radioprotection against the radioactive wastes are demanded.
Further, it is said that miners in uranium ore, coal and metal mines are exposed to more than 6 times as much radiation from the earth's crust as allowed by international recommendations for radiation workers. Moreover, the amount of radiation from outer space (cosmic rays) to which flight crews are exposed is said to be even greater than that to which miners are exposed. Solutions to the problems of radiation exposure in such environments are urgently required.
Besides the specific sources mentioned above, luminous paints on clock or watch faces, glow lamps in fluorescent lamp devices, discharge tubes in displays in gas stations and the like, and smoke detectors in buildings employ isotopes that emit alpha or beta rays. Therefore, proper radiation control is always necessary in sites producing these items.
Thus, with recent industrial development, people are exposed to not only natural radiation such as ultraviolet rays, but also artificial radiation, in daily life and the working environment. Therefore, effective protection of the body from such radiation is required.
To protect internal or external parts of the body (such as the skin, hair, eyes or the like) from ultraviolet rays, one type of radiation, sunglasses with large light-colored lenses, hats with all-round brims with a width of at least 7 cm, dark-colored clothes made of polyester or hemp fibers, and ultraviolet-blocking cosmetics containing titanium oxide are reportedly effective. However, these means block only Ultraviolet-B, which damages DNA in the epidermis of the body, promotes the formation of melanin pigment, rapidly increases active oxygen and thereby ages the tissue cells of the epidermis, and causes skin spots. It is known that Ultraviolet-A penetrates deep into the dermis of the body and cuts or destroys elastic fibers to thereby form unremovable wrinkles or cause cataracts. Further, the recent depletion of the ozone layer allows a large amount of Ultraviolet-C to reach the earth, and thus the effects of Ultraviolet-C pose problems. Thus, protective means against Ultraviolet-A and Ultraviolet-C, in addition to those against Ultraviolet-B, are hoped for.
Moreover, exposure to alpha rays, beta rays, X-rays, gamma rays or like ionizing radiation which penetrates into the human body has not only short-term effects, known as acute disorders, on the human body including the blood and organs, but also long-term effects such as carcinogenesis, genetic damage and the like.
The development of a protective material against the radiation is desired in order to ensure radioprotection of people in general, not just workers in environments where radiation exposure is likely to occur.